So far,synthesis of PtRu black catalyst with high alloying degree and small particle size still remains a big challenge for the practical application in the DMFC.In this work,PtRu black catalysts were synthesized by first loading on a cheap metal oxide-magnesia and then followed a heat-treatment.The role of MgO as the sacrificed support is to prevent the PtRu nanoparticles from aggregation during the heat treatment,thus enabling the acquisition of PtRu black with high alloying degree and small particle size.